Heretofore, for the purpose of improving physical properties of resins, polymer blends and polymer alloys have been actively studied, which are mixtures of resins having different characteristics from each other so as to modify properties of resins. However, among such polymer blends and polymer alloys, when resins having different polarities from each other, for example, a polyolefin such as polypropylene (PP) and a polyamide (PA), are combined together, the poor compatibility between the resins brings about a problem that the resulting composite material has significantly low impact strength.
For this reason, in order to improve the compatibility between polyolefins and polyamides, methods have been proposed, in which a compatibilizer such as a modified polyolefin is used. For example, Japanese Unexamined Patent Application Publication Nos. 2000-327912 (PTL 1) and 2001-302910 (PTL 2) describe a thermoplastic resin composition including a polyamide resin and a modified polyolefin, in which a phase-separated structure has a matrix phase formed of the polyolefin and a dispersed domain formed of the polyamide resin.
Moreover, Japanese Unexamined Patent Application Publication No. Hei 7-97513 (PTL 3) describes a polyamide resin composition including a polyamide resin prepolymer having a relative viscosity within a specific range and modified polypropylene. Japanese Unexamined Patent Application Publication Nos. Hei 7-316423 (PTL 4) and Hei 9-59438 (PTL 5) describe a polyamide resin composition including a polyamide, a modified polyolefin, and an unmodified polyolefin, in which the polyamide forms a matrix phase, and the modified polyolefin and the unmodified polyolefin form a dispersed domain having a core-shell particle structure.
Further, Japanese Unexamined Patent Application Publication No. 2006-307132 (PTL 6) describes a thermoplastic resin composition, in which a dispersed domain having a core-shell particle structure formed of an acid modified elastomer serving as a shell phase and an olefin-based resin component and a filler component serving as a core phase is distributed in a matrix phase formed of a polyamide resin component. Furthermore, Japanese Unexamined Patent Application Publication No. 2010-195853 (PTL 7) describes a thermoplastic resin composition having: a continuous phase (matrix phase) formed of a thermoplastic resin such as a polyamide resin or a polypropylene; a dispersed domain formed of a resin having a reactive functional group; and particulates formed of a reaction product of the thermoplastic resin and the resin having a reactive functional group. However, no conventional polymer blends and polymer alloys have been obtained yet as a resin composition having sufficient physical properties.
Meanwhile, in the fields of automotive interior and exterior components and the like, particularly high mechanical properties are required, and it is essential to satisfy both impact strength and rigidity (flexural modulus). Nevertheless, rigidity and impact strength are conflicting properties. Furthermore, the physical properties of an obtained resin composite tend to be dominated by the physical properties of one of the resins thus combined. Hence, conventional polymer blends and polymer alloys have a problem that it is difficult to satisfy both rigidity and impact strength.